Screw-type cap including an expandable tamperproof strip

ABSTRACT

A screw-type bottle cap having a body with an internal thread and a tamperproof strip which has at least one expansion structure that includes at least one point at which it is fixed to the cap body. In this way, a screw-type cap is produced which has a reliable tamperproof function wherein the tamperproof strip remains attached to the cap body when the cap is unscrewed, without the free ends of the strip protruding from the cap body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plastic screw-type bottle capcomprising a cap body with an internal thread and a tamperproof strip.The latter has flanges disposed on the inside thereof, is non-breakableand is connected by webs to the cap body. As the cap body is unthreadedfrom the bottle the tension or strain in the webs increases causing thelatter to break. The tamperproof strip includes an expansion means withat least one permanent connection disposed in the area between thetamperproof strip and the cap body.

2. Description of the Prior Art

Screw-type caps of this type are widespread and are used in particularon glass or plastic beverage containers. Such bottles are produced in avariety of standard sizes and are circulated in large numbers, either inreturnable or non-returnable form. In particular it is the standardizedbottle neck and accompanying thread in bottles of this type that make itpossible, despite differences in bottle sizes, to employ a uniformscrew-cap. Though this offers many advantages, there is one distinctdisadvantage, in that with the continously large number of bottles incirculation, it is virtually impossible to alter the geometry of thebottle neck. As a result, screw-caps, as so-called disposable articles,must be adapted to the geometry of a given bottle neck or threadconfiguration. Within the bottle-neck-screw-cap system, therefore,modifications are economically feasible only with regard to thescrew-cap.

Known screw-type plastic bottle caps are generally comprised of a capbody with an internal thread and a tamperproof strip. Conventionally,the tamperproof strip is made so that it detaches at least partiallyfrom the cap body when the cap is unthreaded. This is intended as anindication to the consumer that the bottle was either previously opened,or has not yet been tampered with.

Normally, the tamperproof strip is in the form of a ring connected tothe cap body by thin webs. In addition, flange-like elements or lamellaeare provided on the inside of the tamperproof strip which form aso-called stop ring when the cap is screwed on, and which engage thestop ring on the bottle from behind. Such a stop ring is usually formedon the neck of the bottle immediately below the external thread near thebody of the bottle and, in standardized form, has an equivalent orslightly larger diameter than the external thread disposed immediatelyabove it. Due to the slightly conic inclination of the stop ring whereit meets the body of the bottle, the tamperproof strip expandscircumferentially outward somewhat as a result of inherent elasticity ofthe plastic material used. The flanges or lamellae formed on the insideof the strip are thus able to slip past the stop ring and lock in placeonce the cap is completely threaded on, thereby engaging the stop ringfrom behind.

As the bottle is sealed, the flanges or lamellae secure the tamperproofstrip to the stop ring, while webs, designed as predetermined breakingpoints, break as a result of the tension placed on the plastic material.The fractured connection between the tamperproof strip and the cap bodyis a direct indication that the bottle was previously opened.

Tamperproof strips are known in basically two different embodiments. Inthe first tamperproof strip embodiment, the strip detaches completelyfrom the cap body as the latter is unthreaded, and it remains behind asa ring on the neck of the bottle. This embodiment is disadvantageous,however, particularly with regard to waste disposal. Because thetamperproof strip remains on non-returnable bottles, which are melteddown after one use, the resultant melt becomes contaminated. In the caseof returnable bottles on the other hand, the old tamperproof strip mustbe removed prior to refilling and resealing before the new screw-cap canbe attached.

Environmental factors as well do not favor this embodiment, since it isentirely possible that the tamperproof strip stuck initially to the neckof the bottle may become detached and lost in the environment asundesirable litter.

Esthetic considerations, an ever stronger selling point, are a furtherreason against the tamperproof strip remaining on the neck of thebottle, as this is considered a nuisance by many consumers.

The second known tamperproof strip embodiment ruptures when thescrew-cap is removed, but otherwise remains attached to the cap body.Here, the protruding ends of the tamperproof strip are consideredespecially disadvantageous because they are a nuisance to the consumerwhile threading and unthreading the cap, and they may result in bodilyinjury. Esthetic considerations also weigh against the use of thistamperproof strip embodiment, as the protruding ends are found to be anuisance by the consumer.

The closest cited prior art is U.S. Pat. No. 5,246,125. The screw-typecap disclosed therein possesses the features set forth above. Whenthreading and unthreading this screw-cap from the bottle, thetamperproof strip expands in an axial direction due to an expansionmeans and is held in place at a connection point located near saidexpansion means. This action presents serious problems, however, whenthe mold is released during the manufacturing process, because even asthe mold is released a tension is placed on the webs between thetamperproof strip and the cap body, and thus they tend to break duringmanufacturing.

Another screw-type plastic cap is known from German patent publicationDE-A-42 6 123, in which a tamperproof strip is also connected by webs tothe cap body. The tamperproof strip of this screw-cap also has anexpansion means, but it too only expands in an axial direction.

SUMMARY OF THE INVENTION

In light of this background art, therefore, the object of the presentinvention is to provide a screw-type plastic bottle cap comprised of acap body with an internal thread and a tamperproof strip, the latter ofwhich exhibits a more reliable tamperproof function and which remainsattached to the cap body without free ends protruding therefrom.

The object is achieved in that the expansion means, as the cap body isthreaded onto the bottle, uniformly expands the tamperproof strip alongits entire width in a radial direction in such a way that the flangesslip past the stop ring.

A screw-type cap embodiment according to the present invention not onlyresults in a reliable tamperproof function, but also ensures that thetamperproof strip remains attached to the cap body. As the screw-cap isthreaded onto the neck of the bottle, the tamperproof strip expands dueto the conical shape of the stop ring. Together with its flanges orlamellae, the tamperproof strip slips past the stop ring, while the websbetween the tamperproof strip and the cap body are placed under pressureas the latter is threaded, and said webs are therefore unable tofracture.

Conversely, when opening the bottle by unthreading the screw-cap, theflanges or lamellae secure the tamperproof strip initially to the stopring, such that now the webs between the tamperproof strip and the capbody are placed in tension. By further rotating the cap body, thetension in the webs is further increased to the point that the websfinally fracture. The tamperproof strip, however, remains attached viathe permanent connection to the cap body, while further rotating the capbody causes the tension in the tamperproof strip to increase, and theexpansion means on the tamperproof strip to stretch to a point where itis able to slip past the stop ring. At this point the screw-cap may befully unthreaded, in which case the tamperproof strip remains attachedvia the permanent connection to the cap body, and the fractured websbetween the tamperproof strip and the cap body indicate that the givenscrew-cap was activated. Thus, the consumer immediately recognizes thatthe bottle in question has already been opened. Moreover, that thetamperproof strip remains attached to the cap body, helps to circumventproblems of disposal or the environment. Finally, that the tamperproofstrip does not fracture during threading, also prevents protruding stripends from annoying and possible injuring the consumer, and which resultsin an overall more esthetically pleasing screw-type bottle cap.

In accordance with a preferred embodiment of the present invention, theexpansion means has at least two recesses directed substantiallytransversely in the tamperproof strip and which are open ended atopposite edges, respectively of the strip. This allows the tamperproofstrip to expanded in a particularly simple way by stretching it in anaccordion-like manner. Preferrably, the tamperproof strip has twoexpansion means disposed on opposite sides thereof. This allows foruniform expansion of the tamperproof strip in a simple manner, enablingthe strip to slip effortlessly and without snagging past the stop ringas the screw-cap is being threaded.

In a further advantageous modification of the present invention theexpansion means has two recesses arranged on one side of the permanentconnection. This allows for directed expansion of the tamperproof stripfrom one side of the permanent connection.

In another preferred embodiment of the present invention, the expansionmeans has two recesses arranged on opposite sides of the permanentconnection which allows for uniform expansion of the tamperproof stripfrom both sides of the permanent connection.

In yet another preferred modification of the present invention, atamperproof strip is provided without vertical lines of weakening. Inanother words, the former has no predetermined breaking points, as isthe case for instance in screw-caps according to German patentpublication DE-A-42 06 123 and EP-A-0 460 557. In the present embodimentthe tamperproof strip is divided into two functional halves. The firsthalf serves essentially to allow expansion of the tamperproof stripduring the manufacturing process when threaded onto the bottle. Theexpansion step is ensured by undercutting the flanges and by adding anadditional link to the cap body. The first half is capable of extremeexpansion, freely and independently of the second half. The second halfensures essentially that the tamperproof function is reliable. In themanufacturing process expansion is ensured by the expansion means inconnection with a horizontal tie. The purpose of dividing thetamperproof strip into two functional halves is seen in that the secondhalf is required to expand less than the first half. This serves tofurther enhance the reliability of the tamperproof function and tofacilitate resealing of the bottle by the consumer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail below with reference topreferred embodiments, in which

FIG. 1 is a side view of a first embodiment of the screw-type capaccording to the present invention when threaded, and with a partialsectional view through the tamperproof strip,

FIG. 2 is a side view of said first embodiment when threaded withpartial sectional views through the tamperproof strip,

FIG. 3 is a side view of said first embodiment when unthreaded with apartial sectional view through the tamperproof strip,

FIG. 4 is a perspective view of the tamperproof strip of said firstembodiment,

FIG. 5 is a side view of a second embodiment of the screw-type capaccording to the present invention when threaded, with a partialsectional view through the tamperproof strip,

FIG. 6 is a side view of said second embodiment when threaded, with twopartial views through the tamperproof strip, and

FIG. 7 is a side view of said second embodiment when unthreaded with twopartial sectional views through the tamperproof strip.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENT

FIG. 1 is a side view of a first embodiment of the screw-type cap 10according to the present invention. Screw-type cap 10 is comprisedessentially of a cap body 12 and the tamperproof strip 14, and isthreaded onto the neck 30 of a bottle. Tamperproof strip 14 is connectedto the cap body 12 by webs 16 and permanent connection 18. Further, thetamperproof strip 14 is provided with internal flanges 15 and anexpansion means 20. Expansion means 20 has two recesses 22 and 24, eachin the form of a slot. Recess 22 is open at the end proximate the capbody 12, while recess 24 is open at the end proximate the bottle; forthe sake of simplicity, only the neck 30 of the bottle is shown here.

Tamperproof strip 14, shown here in the threaded position, does notexpand and flanges 15 engage stop ring 32 on bottle neck 30 from behind.

FIG. 2 shows said first embodiment of screw-type cap 10 threaded ontobottle neck 30 to a point just before flanges 15 engage stop ring 32.Because of the conical shape of stop ring 32, flanges 15 on tamperproofstrip 14, and thus tamperproof strip 14 itself, are forced radiallyoutward as cap 10 is threaded onto bottle neck 30. As this occurs,tamperproof strip 14 is stretched in an accordionlike manner byexpansion means 20 and recesses 22 and 24, as is shown in FIG. 2.Because cap body 12 of screw-cap 10 presses down on permanent connection18 and webs 16, the latter are placed under pressure and are thus unableto fracture. If the screw-cap is threaded further on bottle neck 30,flanges 15 on tamperproof strip 14 engage stop ring 32, and tamperproofstrip 14 is again contracted. This results in the position of the cap asshown in FIG. 1.

FIG. 3 shows said first embodiment of screw-cap 10 as it is unthreadedfrom bottle neck 30. Flanges 15 which initially abut stop ring 32 securetamperproof strip 14, and with it cap body 12 by way of permanentconnection 18 and webs 16 to bottle neck 30. By further rotating capbody 12, the tension in webs 16 finally becomes so great that the latterfracture. However, tamperproof strip 14 remains fixed via permanentconnection 18 to cap body 12 and tamperproof strip 14 is expanded byexpansion means 20 with recesses 22 and 24, thereby causing flanges 15to slip past stop ring 32. Screw-cap 10 may then be completely removedfrom bottle neck 30 while tamperproof strip 14 remains attached to capbody 12 and without the ends thereof protruding. Due to the fracturedwebs, however, it is immediately apparent that the cap in question waspreviously opened.

Expansion means 20 with recesses 22 and 24 allows tamperproof strip 14to be stretched to a point where bottle neck 30 is once again easilyresealable.

FIG. 4 is a perspective view of tamperproof strip 14 of said firstembodiment. Tamperproof strip 14 has two expansion means 20 locatedopposite one another, each of which includes two recesses 22 and 24,respectively. Said recesses 22 and 24 are formed as slots, each of whichare open-ended at opposite edges, respectively, of the tamperproofstrip. Disposed on the inside of tamperproof strip 14 are flanges 15which are arranged as segments in the present embodiment.

They may however extend continuously along the inside of the strip.Finally, two permanent connections 18 and several webs 16 are formedalong the top edge of tamperproof strip 14.

In said first embodiment according to FIGS. 1-4, vertical lines ofweakening are omitted. This makes further cutting unnecessary in thecase of a cap with a thick tamperproof strip and in which flanges 15 areheavily back tapered. With expansion means 20, extreme expandability oftamperproof strip 14 is assured in the final mold during manufacturingand when threaded onto the neck of the bottle. This process utilizes thenatural resiliency of the plastic materials used. Through selection ofwall thickness within expansion means 20 and cross-section of webs 16,the expansion of tamperproof strip 14 must be properly gauged to avoidfracturing during the manufacturing process, and so that the naturalresiliency of the plastic material used remains optimally intact.

The aforementioned is achieved essentially through the selection of wallthickness in both horizontal links X and Y (FIG. 3) of the expansionmeans. If more than the fracturing of webs 16 is required, extremeexpansion of tamperproof strip 14 and suitable differences in wallthickness between links X and Y may cause link X to break as well. Insuch case, link Y would be thicker than link X.

FIG. 5 shows a second embodiment of a screw-type cap 10 according to thepresent invention. Screw-cap 10 is comprised essentially of a cap body12 and a tamperproof strip 14, and is shown here threaded onto bottleneck 30. Tamperproof strip 14 is attached to cap body 12 by permanentconnection 18 and webs 16. Arranged on the inside of tamperproof strip14 are flanges 15 which in the threaded state, engage stop ring 32 frombehind. Tamperproof strip 14 further includes an expansion means 20,also with two recesses 22 and 24. Recesses 22 and 24 are formed asslots, each being open-ended at opposite edges, respectively, of thetamperproof strip. In contrast to said first embodiment, as shown inFIGS. 1-4, the permanent connection 18 of said second embodiment islocated between recesses 22 and 24.

FIG. 6 is a side view of said second embodiment with a partial sectionalview through tamperproof strip 14 when the cap is threaded, and FIG. 7when the cap is unthreaded. The operation of expansion means 20 wasdescribed in detail above with reference to FIGS. 1-4, hence no furtherdescription thereof is provided here.

In this embodiment as well vertical lines of weakening are omitted.Here, tamperproof strip 14 is divided into two functional halves.

The first half A serves essentially to allow expansion of tamperproofstrip 14 while being threaded onto the bottle during the manufacturingprocess. The expansion step is ensured by undercutting flanges 15, webs16 and link N (FIG. 6). Half A is capable of extreme expansion, freelyand independently of half B. Alternatively, it may be useful to providean additional weak link Z (represented by dashed lines in FIG. 6).

The second half B ensures essentially that the tamperproof function isreliable. During the manufacturing process, expansion is effected byexpansion means 20 in conjunction with horizontal link M (FIG. 6). Withthe difference in wall thickness between links M and Z, substantiallythe same effect is achieved as with the differences in links X and Y insaid first embodiment.

The purpose of dividing the tamperproof strip into two functional halvesA and B is seen in that the second half B is required to expand lessthan the first half A. This serves to further enhance the reliability ofthe tamperproof function and to facilitate resealing of the bottle bythe consumer.

What is claimed is:
 1. A screw cap made of plastic for bottles with astop ring on the neck, comprising a cap body with an internal thread anda tamperproof strip with flanges arranged on the interior surfacethereof, the tamperproof strip being non-breakable and connected to thecap body by webs in which, as the screw-cap is unthreaded from thebottle, tension is increased causing the fracture, and which has anexpansion means with at least one permanent connection provided in thearea of the expansion means between the tamperproof strip and the capbody, wherein the expansion means, as the cap body is threaded onto thebottle, uniformly expands the tamperproof strip along its entire widthin a radial direction in such a way that the flanges slip past the stopring, and said expansion means has at least two recesses which extendsubstantially transversely along the inside of the tamperproof strip andwhich are open-ended at opposite edges, respectively, of saidtamperproof strip.
 2. A screw bottle cap according to claim 1, whereinthe tamperproof strip is provided with two expansion means arranged ondiametrically opposite sides of said strip.
 3. A screw bottle capaccording to claim 2, wherein said expansion means has two recessesarranged on one side of the permanent connection.
 4. A screw bottle capaccording to claim 2, wherein said expansion means has two recessesarranged on opposite sides of the permanent connection.
 5. A screwbottle cap according to claim 1, wherein said tamperproof strip isformed without vertical lines of weakening.